Nishikori, last year's runner-up, upset by Paire at US Open

NEW YORK (AP) -- A year after his run all the way to his first Grand Slam final, Kei Nishikori's stay at the U.S. Open lasted only a few hours.

The fourth-seeded Nishikori had two match points in the fourth-set tiebreaker against 41st-ranked Benoit Paire, but the Frenchman saved both of them then took control in the fifth for a 6-4, 3-6, 4-6, 7-6 (6), 6-4 victory Monday.

It was the first win of his career against an opponent ranked in the top five.

"When I saw the draw against Kei, I said, 'Bad luck,'" Paire recalled.

But then he reminded himself he had been competitive in two previous losses to the Japanese star.

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"It's not like if I play against Roger Federer," Paire said, explaining he knew he could get something going against Nishikori's serve. "Against Kei, I know I can play."

Nishikori had withdrawn from the hard-court warmup at Cincinnati, citing a hip injury, but he said Monday he was fine physically. Still, he looked sluggish late in the match, which lasted 3 hours, 14 minutes on a steamy day.

"He was very aggressive, so there was many rallies and it was tough to get rhythm," Nishikori said. "He hits a lot of drop shots and good serves."

Last year at Flushing Meadows, Nishikori became the first man from Asia to reach a major final, where he lost to Marin Cilic.

The 25-year-old followed that up with more success in 2015 and came into the U.S. Open with his first top-four seed at a Grand Slam tournament. He made it to the quarterfinals at both the Australian and French Opens this year, but withdrew from the second round at Wimbledon because of a calf problem, the latest injury in a career plagued by them.

He had been playing well on the hard courts this summer before pulling out of Cincinnati, though, winning the title at Washington and beating Rafael Nadal in Montreal, where he lost to eventual champ Andy Murray in the semifinals.

It's the first time since 1999 that a U.S. Open men's finalist lost in the first round the following year. Cilic had no such problems Monday, starting his title defense with a straight-set victory over 94th-ranked qualifier Guido Pella.

The 26-year-old Paire has never been past the third round at a major tournament. He had 21 aces Monday, the last to close out the match.

Novak Djokovic and Rafael Nadal were playing later Monday.

On the women's side, four of the top 10 players are already out, with seventh-seeded Ana Ivanovic, eighth-seeded Karolina Pliskova and 10th-seeded Carla Suarez Navarro losing Monday, a day after third-seeded Maria Sharapova withdrew. All were on Serena Williams' half of the draw.

Williams opens her pursuit of the first Grand Slam since Steffi Graf in 1988 on Monday night in Arthur Ashe Stadium. Before she even steps on the court, not a single top-10 player stands in the way between the American and the final.